1. Field of the Invention
The present invention relates to an ozonizer for generating ozone by a silent discharge caused by applying AC high voltage. More particularly, it relates to an ozonizer wherein an ozone generating efficiency is highly improved by minimizing a discharging gap between a ground electrode and a high voltage electrode tube.
2. Description of the Prior Arts
FIG. 1 shows the conventional coaxial cylindrical type ozonizer wherein the reference numeral (1) designates a cylindrical casing which comprises a grounding metal tube (2) having a jacket having a cooling water inlet (9) and a cooling water outlet (10) and an inlet 11 of a raw material gas such as air or oxygen and an outlet of an ozonized gas (12); (4) designates a high voltage electrode tube made of a dielectric material such as glass which is coaxially disposed in the grounding metal tube (2) by means of a plurality of spacers (13) to form a specific discharging gap space (3); (5) designates an electric conductive film formed on an inner surface of the electrode tube; and (6) designates a feeder for applying AC high voltage from a feeding line (7) through a bushing (8) to the electric conductive film (5). Many pairs of the grounding metal tubes (2) and the high voltage electrode tubes (4) are disposed in the cylindrical casing (1) depending upon the required ozone generating capacity.
When the AC high voltage is applied to the high voltage electrode tube (4) in the conventional ozonizer, a silent discharge or mild glow discharge is formed in the discharging gap space (3) whereby the raw material gas fed into the tube is ozonized.
The ozone generating efficiency .eta. is given by the equation EQU .eta.=Y.sub.O.sbsb.3 /W
wherein W represents a discharge power and Y.sub.O.sbsb.3 represents an ozone generating rate. The ozone generating efficiency .eta. is increased by reducing the discharging gap space (3). When the discharging gap distance d is reduced, the probability by dissociating an oxygen molecule of electrons is increased whereby "a discharging effect" for generating effectively ozone is improved. The decomposition of ozone is controlled by improving the cooling effect in the discharging gap space (3) whereby "a cooling effect" for effectively producing ozone is improved.
Recently, it has been required to reduce the cost of an ozonizer and the operating cost thereof depending upon an increase of a capacity of the ozonizer. In order to reduce the operating cost, that is to improve the ozone generating efficiency .eta., it is necessary to reduce the discharging gap distance as described.
In order to reduce the discharging gap distance, it has been required to use the dielectric tube and the metal grounding electrode having higher accuracy and accordingly, an expensive ozonizer is required. Accordingly, in the conventional ozonizer, the discharging gap distance has been usually several millimeters from the viewpoint of the cost of the ozonizer, and a further improvement for improving the ozone generating efficiency .eta. has been required.